Transformer switch with improved rotary axial bridging contact structure

ABSTRACT

A switch adapted to be disposed within the casing of an electrical distribution transformer, which may be connected as a series-multiple switch, or as a tap changing switch. The switch includes a stator portion having a contact deck with a plurality of stationary contacts arranged in two spaced planes, and a rotor portion having electrically connected contacts disposed to engage stationary contacts in both planes.

United States Patent [72] Inventor Donald J. Ristuccia [56] References Cited Athens, UNITED STATES PATENTS $3 i 1970 1,739,003 12/1929 Klingensmith -200/11 (A) [45] Patented g 1971 2,880,284 3/1959 Laete 200/16 3,174,000 3/1965 Golbeck ZOO/ll (D) [731 ga g z Elem" CmPanY 3,313,904 4/1967 Chambaut 200/11 1) s 3,371,167 2/1968 Soulakis,.lr. 200/166(BH) 3,525,827 8/1970 Allison 200/11 (D) [54] TRANSFORMER SWITCH WITH IMPROVED Primary Examiner-J. R. Scott ROTARY AXIAL BRIDGING C NTACT Attorneys-A. T. Stratton, F. E. Browder and Donald R. STRUCTURE Lackey 16 Claims, 9 Drawing Figs. [52] s 'x-" -a fay ABSTRACT: A switch adapted 16 be disposed within the ms In 4 19/58 ing of an electrical distribution transformer, which may be Holhl 26 connected as a seriesmumple Switch. or as a tap Changing Field of Search zoo/8 1 switch. The switch includes a stator portion having a contact deck with a plurality of stationary contacts arranged in two spaced planes, and a rotor portion having electrically connected contacts disposed to engage stationary contacts in both planes.

PATENTEU NUVBOIHYI SHEET 1 OF 4 $524,319

INVENTOR Donald J. Ristuccio PATENTEUNBV30I97| 3,624,319

SHEET 3 OF 4 ugu TRANSFORMER SWITCH WITI-I IMPROVED ROTARY AXIAL BRIDGING CONTACT STRUCTURE BACKGROUND OF THE INVENTION I Field of the Invention The invention relates in general to electrical switches, and more specifically, to an electrical switch which is adapted to be disposed within the casing of an electrical distribution type transformer.

2. Description of the Prior Art Many distribution transformers are purchased by electrical utilities with series-multiple switches, which are externally operable no-load switches disposed within the transformer tank, and connected to certain windings or coil sections of the transformer which are connected either in series, or in parallel, by the switch. Thus, the electrical utility is free to change the magnitude of the voltage applied to the distribution transformers in the future, without the necessity of changing all of the distribution transformers connected to the system. Since the series-multiple switch is operated only at the time of a system voltage changeover, it is a no-load type switch, and although it does not have to be constructed to allow a large number of mechanical operations, it must be extremely reliable.

The different system voltages of the electrical utilities, along with the different preferences of the utilities, have resulted in a large number of different series-parallel circuit arrangements. For example, two separate coils, one with a tap, may be interconnected, or three separate coils without taps may be interconnected, or three separate coils with one having a tap may be interconnected, with some of the tapped three coil arrangements requiring a three position switch instead of the conventional two position switch. Further, some arrangements have no protective links, others have two, and still others have four.

The series-parallel switch should be versatile enough to accommodate these different arrangements with a single contact deck for most single-phase applications, and it must be easily ganged for use with polyphase applications. Further, the switch must accomplish the required versatility without substantially increasing the manufacturing cost of the switch, compared with less versatile switches of the prior art, and it is imperative that the switch be small and compact, since increasing the tank size to accommodate a versatile switch would offset any potential savings therein, due to the increased cost of the tank, and the increased cost of the additional cooling and insulating fluid required to fill the larger tank, which would also deleteriously affect the shipping weight and shipping cost of the apparatus.

It would also be desirable to construct the series-multiple switch with the versatility of enabling it to be used as an externally operable, no-load tap changer for distribution type transformers, which would therefore make it unnecessary to manufacture different switches for series-multiple use and for tap changing use.

SUMMARY OF THE INVENTION Briefly, the present invention is a new and improved rotary, direct action, no-load switch which has the large number of stationary contacts required to enable it to be used for any multiple voltage switching requirement, or as a no-load tap changer for distribution transformers. The switch includes a small, compact stator portion having a single contact deck suitable for most single-phase applications, with a full I25 kv. BIL being maintained between stationary contacts disposed on the contact deck by placing the contacts in two spaced planes. The contacts of one plane are circumferentially spaced by a predetermined dimension, and the contacts of the other plane are oriented to fall midway between predetermined adjacent contacts of the first plane, to provide the required insulating clearance with minimum spacing of the two planes. Disposing the contacts in two planes substantially reduces the diameter of the switch, compared with a switch of similar rating having the same number of contacts disposed in a single plane, and the circumferential staggering of the contacts from plane to plane reduces the overall length of the switch.

The rotor portion of the switch is directly operated by a shaft which extends through the wall of the associated transformer tank, and it carries two movable contact assemblies, each of which include electrically connected contact elements oriented to engage stationary contacts in both planes, as the operating shaft is rotated.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and uses of the invention will become more apparent when considered in view of the following detailed description of exemplary embodiments thereof, taken with the accompanying drawings, in which:

FIG. I is a side elevational view, partially in section, of an electrical switch constructed according to the teachings of the invention;

FIG. 1A is a perspective view of a stationary contact element for the switch shown in FIG. 1;

FIG. 2 is an end view of the switch shown in FIG. 1, taken in the direction of the operating handle side of the switch;

FIG. 3 is an end view of the switch shown in FIG. 1, taken in the direction of the contact side of the switch;

FIG. 3A is a perspective view of the rotor portion of the switch shown in FIG. 1;

FIG. 3B is a perspective view of one of the contact assemblies for the rotor shown in FIG. 3A;

FIG. 4 is a side elevational view of a three-phase embodiment of the switch shown in FIG. I; and

FIGS. 5A and 5B are schematic diagrams which illustrate a typical series-multiple switching application for the switch shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and FIGS. 1, 2 and 3 in particular, there is shown side, left end and right end elevational views, respectively, of an electrical switch 10 constructed according to the teachings of the invention. Switch 10 may be used as a series-multiple switch, to change coil connections within a distribution transformer when the electrical utility changes the distribution voltage applied to the transformer, or as a tap changing switch connected to a winding of a distribution transformer to set the output voltage of the transformer at the time of installation according to the characteristics of the connected load, and also to enable adjustments to be made in the output voltage at some future date. This versatility requires a large number of stationary contacts which are spaced to meet the required BIL rating, and which are physically able to carry the required current without overheating. Switch 10 provides these functions at a relatively low cost, and without taking up much space within the transformer tank.

More specifically, switch I0 includes a stationary or stator portion 12, and a rotatable or rotor portion 14, with the latter being positioned within stator 12 for rotational movement relative thereto.

The stator portion 12 includes a mounting hub 16, a substantially ring-shaped contact deck 18, and a plurality of circumferentially spaced rib members 20, 22, 24 and 26 which space the hub 16 and contact deck 18, and maintain the desired alignment between them. The mounting hub 16 has first and second ends 28 and 30, respectively, and an opening 32 which extends between its ends. The axis of opening 32 is coaxial with the axis of the contact deck 18, forming a central axis 34 of the switch 10.

The mounting hub 16 includes a metallic stator insert member 36 which may be economically die cast of aluminum or brass with the desired physical details. Insert member 36 is molded into an insulating structure which completes the mounting hub 16 and also forms the contact deck 18 and the connecting rib members. A glass filled polyester resin has been found to be a suitable molding material, but any molding material which will have the required resistance to the transformer insulating and cooling dielectric fluid may be used. Thus, the first end 28 of mounting hub 16 is provided by the metallic insert member 36, and the second end 30 is formed by the molded insulating material, with the embedded end of insert member 36 being suitably ribbed or grooved to insure that the insert 36 will be securely fixed within the molded assembly.

Mounting hub 16 has a plurality of threads 31 disposed on its outer surface adjacent end 28, and a mounting flange 38 disposed between its ends 28 and 30 which has a flat surface perpendicular to the central axis 34, with the flat surface facing end 32 of the mounting hub. An annular groove 40 is disposed in the flat surface of flange 38, for receiving a gasket member 42. Groove 40 is disposed in flange 38 such that there are flat surfaces on both sides of the groove, i.e., surfaces 44 and 46, with these flat surfaces being in alignment. End 28 of mounting hub 16 is disposed through an opening in the casing of its associated distribution transformer, with the opening in the transformer casing being sized such that the casing contacts both surfaces 44 and 46. A longitudinal groove 33 through the threaded portion of the stator insert 36 cooperates with a projection in the opening of the transformer tank to properly orient the switch relative to the transformer tank, and also prevent it from turning in the opening during the operation of the switch. The transformer tank wall is illustrated by broken line 48. When the switch I is mounted in a tank wall of its associated transformer, the nut (not shown) disposed on threads 31 may be tightened until a metal-tometal contact is made between the casing and surfaces 44 and 46. The dimensions of the annular groove and of the gasket member 42 are selected such that when metaI-to-metal contact is obtained, the gasket will be properly stressed. This structural arrangement simplifies the installation of the switch 10, as the gasket compression is determined by the accurate dimensions of the die cast insert 36, and not by assembly personnel instructed to tighten the mounting nut with a predetermined number of inch pounds of torque.

End 28 of the mounting hub 16, which extends outside the transformer tank when the switch is mounted therewith, has first and second outwardly extending pinlike members 50 and 52, which, as will be hereinafter explained, provide stops for limiting the rotary movement of the switch. End 28 also has a plurality of circumferentially spaced blind openings 54, 56, 58, 60 and 62 disposed therein, which may be used to lock the switch 10 in the desired position, and blind openings 64 and 66, which may be used to further restrict the rotary movement of the switch 10, with both features being more fully explained hereinafter.

In order to provide the desired versatility for accommodating any practical series-multiple switching arrangement, as well as to enable the switch 10 to be used as a no-load tap changing switch, a large number of stator contacts are required, with the switch 10, in this example, having a provision for including 12 stationary contacts. Contact deck 18 carries the stationary contact members, but instead of disposing all of the stationary contacts in a single plane, they are disposed in two spaced planes, indicated by lines 68 and 70. The stationary contacts must be a certain minimum distance apart, in order to meet the required BIL rating, with the switch 10 being constructed to provide a rating of I kv. BIL between the stationary contacts. If all of the stationary contacts were to be placed in a single plane, it would require a prohibitively large switch diameter, which would interfere with other components in the transformer tank unless the tank were to be made larger to accommodate the switch. Increasing the tank size, however, would offset any advantage a versatile switch construction would provide, due to the increased manufacturing cost of the tank and the increased amount of cooling and insulating fluid, such as mineral oil, which will be required to fill it, Thus, there is a certain maximum diameter which the switch 10 may assume without dictating a large tank, and this diameter, along with the necessary clearance between contacts is used to set the number of contacts disposed in the first plane 68. In this example, for I25 kv. BIL, eight stationary contacts 72, 74, 76, 78, 80, 82, 84 and 86 are disposed in the first plane 68 of the contact deck 18, and four contacts 88, 90, 92 and 94 are disposed in the second plane 70. The contacts of the first plane 68 are uniformly spaced, and each of the contacts of the second plane are oriented to fall midway between certain adjacent contacts of the first plane. The longitudinal center line of the stationary contacts intersect at the central axis 34 of the switch 10. The longitu dinal center lines of two adjacent stationary contacts on plane 68, such as longitudinal center lines 96 and 98 of stationary contacts 84 and 82, respectively, form an angle I00 between them, which angle is bisected by the longitudinal center line 102 of contact 94 in the second plane 70, when the longitudinal center line of contact 94 is projected into the first plane. In the example, the stationary contacts of the first plane are 45 apart. Thus, the stationary contact of the second plane is placed to form two 2259 angles between the three contacts. By placing the contacts of the second plane 70 midway between the contacts of the first plane 68, the required clearance between the contacts of the two planes may be obtained with a minimum spacing 104 between the planes.

The stationary contacts, shown most clearly in FIG. 1A, which is a perspective view of a stationary contact, such as stationary contact 72, are formed of a good electrically conductive material, such as copper. Contact 72 has an elongated, substantially rectangular configuration, having first and second ends 106 and I08, and opening 109 disposed approximately midway between the ends of the contact, and predetermined width and thickness dimensions selected to carry the current magnitude of the specific application. The open construction of stator 12 enable free flow of the transformer coolant about the switch contacts, thus enabling the'physical size of the stationary and movable contacts to be reduced, compared with arrangements where the contacts are blocked from receiving a free flow of coolant.

The first end 106 of the stationary contact faces inwardly from the contact deck 18, and is the portion of the contact which engages the movable contact. Both major surfaces of the stationary contact adjacent the first end 106 have a Iongitudinal depression therein which bisects the width of the contact, such as provided by slot 110, with these depressions cooperating with the movable contact to provide a detent action, as will be hereinafter explained.

The second end 108 of contact 72 extends outwardly from the contact deck 18, and electrical leads from the transformer coil sections are connected thereto, such as by using a crimp type connector. Since in many instances it is desirable to connect two leads to a single stationary contact, end 108 may be longitudinally out along its center line for a predetermined dimension, forming first and second terminals 112 and I14 which are bent away from the major plane of the contact, in opposite directions, to enable an electrical lead to be attached to each terminal, if required, with crimp type connectors.

The stationary contacts are located or oriented on contact deck 18 by raised guides which are integrally molded therewith, and which are spaced to snugly accept the width dimension of the stationary contacts, with openings being disposed between the raised guides perpendicularly through the contact deck. The opening through a stationary contact is aligned with the opening disposed between the guides and the stationary contact is held in place by a rivet disposed through the aligned openings. For example, as best shown in FIG. 3, stationary contact 82 of the first plane is placed between raised guide members 116 and 118 and fixed in position by a rivet 120, which automatically orients the longitudinal center line of the contact to intersect the central axis 34 of the switch 10. The stationary contacts of the second plane 70 are supported on integrally molded projections which have raised guides on their outwardly extending ends, similar to the guides for orienting the stationary contacts of the first plane 68. For example, as best shown in FIG. 1, stationary contact 94 is fixed to the end of projection 122 and oriented by raised guide members 124 and 126.

The rotor portion 14 of switch 10, shown in elevation in FIGS. 1 and 3, and in perspective in FIG. 3A, includes a metallic shaft portion 130, an insulating contact carrier portion 132, and first and second movable contact assemblies 134 and 136, respectively. Shaft member 130, which may be machined of a noncorrosive material, such as brass, has a first end 138, and a second end embedded in the insulating contact carrier 132. The embedded portion of shaft 130 may be knurled to enhance the adhesion of the molded material thereto. A transverse opening 140 is provided through shaft 130 near end 138, and first and second spaced circumferential grooves 142 and 144 are provided in the exposed portion of the shaft.

The insulating contact carrier 132 may be formed of any suitable material which will operate satisfactorily in the transformer cooling and insulating dielectric, with a glass filled nylon being suitable, and it is molded to accept the first and second contact assemblies 134 and 136, and also to provide a circular projection 146 at its extreme end 148, with the axis of the circular projection 146 being coaxial with the longitudinal axis of shaft 130.

The movable contact assemblies 134 and 136 are of similar construction, with movable contact assembly 134 being shown in perspective in FIG. 38. Contact assembly 134 is constructed of first and second mating parts 150 and 152 which provide first, second and third contact elements 154, 156 and 158, respectively, each having first and second fingerlike" contacts which are biased together by the mating two-piece construction of the assembly.

The mating parts 150 and 152 are formed of a good electrical conductor having the desired springlike characteristic, such as beryllium-copper, or the like. Each of the mating parts has three arms, with part 150 having arms I60, I62 and 166. Arms 160 and 162 are disposed in the same plane, with the longitudinal axes of the two arms forming an angle 164 which is the same as the angle 138 shown in FIG. 2 between two adjacent stationary contacts of the first plane. Arm 166 is electrically connected to arms 160 and 162 via the depending member 161, but is disposed in a second plane parallel with the first plane, and spaced from the first plane by the dimension 104 between the planes 68 and 70 shown in FIG. 1. Further, the longitudinal center line of am 166 bisects the angle 164 formed between arms 160 and 162, when it is projected into the first plane. Arms 160, 162 and 166 have a length dimension selected such that when assembled with their contact carrier 132, they will overlap the inwardly extending stationary contacts by a predetermined dimension.

The second mating part 152 is similar to the first mating part 150, except for the construction of the extreme ends of their contact arms, with like components of the two parts having like reference numerals, except the reference numerals of mating part 152 have a prime mark to distinguish them from part 150.

The outwardly extending ends of the contact arms, which form the contact fingers of the three contact elements 154, 156 and 158, are each bent along a longitudinal line which bisects their width dimensions, with this line having a predetermined dimension starting at the extreme end thereof, providing a substantially V-shaped cross-sectional configuration for the bent portion of the contact arm. The contact anns of the two mating parts are bent in opposite directions, such that the common edges of the two legs of the V-shaped configuration of the two mating parts contact one another, providing an end view of each contact element which resembles the letter X,

Each movable contact assembly, such as assembly 134, has openings through the three contact arms of each mating part, such as openings 172, 174 and 176, which cooperate with openings disposed in the contact carrier 132, with rivets being placed through the openings to firmly secure each movable contact assembly to the rotor portion 14 of the switch 10. The contact assemblies 134 and 136 are fixed to opposite sides of the contact carrier 132, such that the longitudinal centerlines of the contact elements of one movable contact assembly are each aligned with one of the longitudinal center lines of a contact element of the other movable contact assembly.

In the assembly of the rotor 14 and the stator 12, O-ring members 178 and 180 are placed on shaft I30 in the circumferential grooves 142 and 144, respectively, and then the end 138 of shaft member is inserted into opening 32, starting at end 30 of the mounting hub. The O-ring members 178 and provide shaft seals when they are compressed by the inner wall of the mounting hub, preventing leakage of the transformer coolant. The flange 182 formed at the termination of the contact carrier 132 adjacent the exposed portion of shaft member 130, rests against end 30 of the mounting hub 16 to provide a positive longitudinal location for the rotor 14 relative to the stator 12. The rotor 14 is secured in this position, and a rear bearing for the assembly formed, by a member 184 which has an opening therein sized to receive the circular projection 146 on the end of the contact carrier, with member 184 being secured to mounting tabs disposed on the contact deck 18, such as mounting tabs 186 and 188 which are formed integrally with the contact deck. The contact deck may have an additional plurality of mounting tabs, which may be used to connect a plurality of contact decks together for polyphase applications, as will be hereinafter explained. Member 184 is shown in fragmentary form in FIG. I, in order to more clearly illustrate the construction of the switch, but it is shown in full, connected to the mounting tabs, in the polyphase embodiment of the switch illustrated in FIG. 4, referenced 226.

An operating handle 190, shown in section in FIG. 1, and in full in FIG. 4, is pinned to the end of shaft 130, using the opening I40 and a similar opening through the sides of the operating handle. Handle 190 has a pointer end 192 and a handle end 194. The operating handle 190 has a steppedlike construction, having a first portion 196 which is closely adjacent end 28 of the mounting hub, and a second portion 198 which steps outwardly away from the mounting hub. This construction of the operating handle 190 enables portion 196 to cooperate with the stop members or pins 50 and 52, as shown in dotted outline in FIG. 2 at each end of the rotary range, to limit the rotary movement of the rotor 14. Thus, as illustrated in the figures, switch 10 may have five operating positions between the two stops 50 and 52, with the five operating positions being required in the event the switch is used as a noload tap changer for a distribution transformer. Portion 198 of handle 190 clears the stops 50 and 52, thus allowing the handle to be turned through approximately 180.

When switch 10 is used as a series-multiple switch, most applications will only require two positions, but some applications require three. A two position switch is obtained by placing a pin in opening 66, with the pin having a length sufficient to strike the side of the handle portion 194. Placing the pin in opening 64 instead of opening 66, provides a three position switch,

Switch 10 may be locked in the desired position by threading a screw through a tapped opening disposed through the operating handle 190, such as through opening 199, which opening is aligned with one of the openings 54, 56, 58, 60 and 62, depending upon the operating position of the switch. The screw extends into the blind opening disposed in the end of the mounting hub, thus preventing the turning of the switch to a new position.

When the rotor 14 is assembled within the stator portion 12, turning the operating handle moves the movable contact elements 154, 156, 154 and I56, in the first plane 68, and it moves the movable contact elements 158 and 158 in the second plane 70. The contact fingers of the movable contact elements are forced apart by the stationary contacts with a desirable wiping action, when the switch is operated to change positions, and the contacts engage with a detent when the edges of the V-shaped fingers snap into the longitudinal depressions or slot in the stationary contacts. Thus, a feel" is provided which enables operating personnel to tell when proper engagement between the stationary and movable contacts is obtained.

The switch 10 shown in FIGS. 1, 2 and 3 lends itself to ganging for providing more than one deck. More than one deck may be necessary in single-phase applications when the current requirements require paralleling the contacts, in singlephase applications where the series-multiple circuit arrangement has an unusually large number of coil sections to be interconnected and switched, and in three-phase applications. FIG. 4 is an elevational view of a switch 200 having three decks such as would be used for a three-phase application. Like reference numerals in FIGS. 1, 2, 3 and 4 indicate like components.

Switch 200 is mounted through the sidewall portion 201 of a distribution transformer, and is fixed in position by a washer member 203 and lock nuts 205. An operating handle 190 is fixed to the end of the operating shaft, in the manner hereinbefore described relative to the switch 10 shown in FIG. 1.

Switch 200 includes first, second and third decks 202, 204 and 206, respectively, with each deck including a stator and rotor portion. The first deck 202 includes a stator portion 12 and a rotor portion 14, which are similar to those hereinbefore described relative to switch 10. Two additional ring-shaped contact decks 208 and 210 are provided, which are similar to contact deck 18 of the first deck 202, and they are bolted to the first contact deck 18 using structural insulating members 212, 214, 216 and 218, which extend past mounting tabs on the decks, and which have openings therein oriented with the openings in the mounting tabs. For example, the structural member 218 is bolted to mounting tabs 186, 217 and 219 by the nut and bolt assemblies 221, 223 and 225, respectively.

The second and third decks 204 and 206 have rotors 220 and 222, respectively, which are similar to rotor 14 of the first deck, except the metallic operating shaft is not required on the additional rotors, and a blind opening is disposed in the end of the contact carrier which normally would carry the metallic operating shaft. The blind opening is sized to receive the circular projection at the extreme end of the contact carrier. The circular projection 146 on the first rotor is inserted into the blind opening in rotor 220, with the projection 146 having an opening therein which is aligned with an opening in rotor portion 220, with the alignment being fixed and maintained by a pin 209 disposed through the openings. In like manner, the second rotor 220 has a circular projection 211 which cooperates with a blind opening in the third rotor 222. Rotor 220 is fixed to rotor 222 by a pin member 213 disposed through aligned openings in the circular projection 211 and in the rotor portion 222. Rotor portion 222 has a circular projection 224 which cooperated with an opening in a structural member 226, to provide a rear bearing for the stack of assembled rotors, as well as to prevent longitudinal movement of the rotor assembly. One end of structural member 226 is connected to a mounting tab on the third deck via nut and bolt combination 227, and the other end is connected to the mounting tab 219 of the same deck via the nut and bolt combination 225.

Thus, switch 200 may be quickly and easily constructed from the same basic parts used with the switch 10, to provide a compact multideck switch, which will handle three-phase assignments, or unusual single-phase applications. Switch 200 may be used as a five position tap changing switch, or by disposing a pin 207 in one of the blind openings 64 or 66 in the front of the mounting hub, switch 200 may be made into a two or a three position series-multiple switch.

FIGS. A and 5B are schematic diagrams of the switch shown in FIG. I, mounted in an electrical distribution transformer tank and connected to switch a plurality of primary coil sections from a parallel arrangement in a first switch position, to a series arrangement in a second switch position. Since switch 10, in this example, is a two position switch, a blocking pin would be inserted in opening 66 of the first end 28 of the mounting hub 16.

Switch 10 is mounted in sealed relation through the sidewall portion of a distribution transformer, with the end 28 of the mounting hub and operating handle I disposed external to the tank, and the contact structures immersed in the transformer coolant inside the tank. Transformer 230 has a primary winding 232 disposed in inductive relation with a magnetic core 234, with winding 232 having first, second and third coil sections 236, 238 and 240, each having first and second ends represented by the left and right-hand terminals disposed on the sections. The secondary winding is not shown.

The high voltage bushings, represented by terminals 242 and 2, are each connected to one of the stationary contacts and to one end of different coil sections. For example, ter minal 242 may be connected to stationary contact 88 on the second plane 70, and to the first end of coil section 240. Terminal 244 may be connected to stationary contact 92 on the second plane, and to the second end of coil section 236. The first end of coil section 236 is connected to stationary contacts 72 and 84, the first end of coil section 238 is connected to stationary contact 74, the second end of coil section 238 is connected to stationary contact 82, and the second end of coil section 240 is connected to stationary contacts 76 and 80.

In the position of switch 10, shown in FIG. 5A, the movable contact assembly 1136 connects the first ends of the coil sections 236, 238 and 240 to terminal 242, and movable contact assembly 134 connects the second ends of the coil sections to terminal 244. Thus, in this position of switch 10, all of the coil sections are connected in parallel between the two input terminals.

In the position of switch 10 shown in FIG. 5B the coil sections 236, 238 and 240 are serially connected. The circuit enters tenninal 244 and traverses the first coil section 236, proceeds to the second end of the second coil section 238 via stationary contacts 84 and 82 of the movable contact assembly 134, it traverses coil section 238 and enters the second end of coil section 240 via stationary contact members 74 and 76 of the movable contact assembly 136, it traverses coil section 240, and then proceeds to the terminal 242.

In summary, there has been disclosed a new and improved switch for distribution transformers which has the versatility of being able to handle any series-multiple arrangement, single or polyphase, as well as the ability to function as an externally operable no-load tap changer. The switch is direct acting, eliminating the extra cost and space required by operating linkages, and it is small and compact, while maintaining the necessary clearances between parts of different electrical potential, to provide the required kv. BIL rating between contacts. Despite the versatility of the switch 10, it may be easily and economically manufactured and assembled. The contact structure and arrangement provides a wiping action upon operation of the switch, which cleans the contacts of any oxide which may have been built up thereon, and a detent action is provided which creates a noticeable feel" when the switch is operated, to notify operating personnel when the contacts are properly engaged. Switch 10 is easy to mount and connect, as the electrical leads from the transformer coil sections may be crimped directly to the switch terminals, eliminating the necessity of providing a switch with electrical leads extending from its terminals which must be crimped to leads from the coil, and the proper hermetic tank seal is obtained without danger of overcompressing the sealing gasket, by a metal-to-metal seal construction which includes a gasket disposed between the switch and tank, which is automatically stressed by a predetermined amount by the construction of the parts, rather than by the skill of the assembly personnel.

I claim:

1. An electrical switch for use with a distribution transformer, comprising:

a stator portion having a central axis, a ring-shaped contact deck coaxial with the central axis, and a plurality of stationary contacts arranged on said ring-shaped contact deck in first and second spaced planes perpendicular to the central axis, provided by a substantially planar surface of said ring-shaped contact deck, and the ends of a plurality of circumferentially spaced projections on the planar surface, respectively, said stationary contacts having an elongated configuration with their ends extending radially inward and outward from said ring-shaped contact deck,

and a rotor portion coaxially positioned within said stator portion for rotational movement relative thereto, said rotor portion having first and second contact assemblies each having first, second and third electrically connected contact elements, the first and second contact elements of each contact assembly are disposed to engage the inwardly extending ends of the stationary contacts disposed in one of the planes, and the third contact element of each contact assembly is disposed to engage an inwardly extending end of a stationary contact disposed in the other plane, when said rotor portion is rotated relative to said stator portion.

2. The electrical switch of claim 1 wherein the stationary contacts of the first plane are circumferentially spaced about a firs circle coaxial with the central axis of the stator portion, and the stationary contacts of the second plane are disposed about a second circle coaxial with the first circle, with the contacts of the second plane being located on a line which is midway between certain of the stator contacts of the first plane.

3. The electrical switch of claim 2 wherein the first and second contact elements of each of the first and second contact assemblies are spaced to simultaneously engage two circumferentially adjacent stationary contacts of one of the planes, and the third contact element of each of thefirst and second contact assemblies is disposed midway between the first and second contact elements, but axially spaced therefrom, to engage a stationary contact of the other plane when one is disposed between the two stationary contacts engaged by the first and second contact elements of the contact assembly.

4. The electrical switch of claim 1 wherein the stationary contacts have first and second ends, with the first end being a knife blade type contact, and wherein the contact elements of the first and second contact assemblies each include two fingerlike contacts biased together, said knife blade type stationary contact forcing the fingerlike contacts of the contact elements apart when in engagement therewith.

5. An electrical switch for use with a distribution transformer, comprising:

a stator portion having a central axis, and a plurality of stationary contacts arranged about the central axis in first and second spaced planes perpendicular to the central axis,

and a rotor portion coaxially positioned within said stator portion for rotational movement relative thereto, said rotor portion having first and second contact assemblies each having first, second and third electrically connected contact elements, the first and second contact elements of each contact assembly are disposed to engage stationary contacts disposed in the first plane, and the third contact element of each contact assembly is disposed to engage stationary contacts disposed in the second plane, when said rotor portion is rotated relative to said stator portion,

said stationary contacts having first and second ends, with the first end being a knife blade type contact, and wherein the contact elements of the first and second contact assemblies each include two fingerlike contacts biased together, said knife blade type stationary contact forcing the fingerlike contacts of the contact elements apart when in engagement therewith, said fingerlike contacts of the contact elements being substantially V-shaped and the stationary contacts having depressions therein which cooperate with the bottom edges of the V-shaped fingerlike contacts to provide a detent action when the contacts engage.

6. An electrical switch for use with a distribution transformer, comprising:

a stator portion having a central axis, and a plurality of stationary contacts arranged about the central axis,

and a rotor portion coaxially positioned within said stator portion for rotational movement relative thereto, said rotor portion having first and second contact assemblies each having first, second and third electrically connected contact elements, the first and second contact elements of each contact assembly are disposed to engage stationary contacts disposed in the first plane, and the third contact element of each contact assembly is disposed to engage stationary contacts disposed in the second plane, when said rotor portion is rotated relative to said stator portion,

said stationary contacts having first and second ends, with the first end being a knife blade type contact, and wherein the contact elements of the first and second contact assemblies each include two fingerlike contacts biased together, said knife blade type stationary contact forcing the fingerlike contacts of the contact elements apart when in engagement therewith, the second ends of the stationary contacts each being divided to provide two terminals adapted for connection to external electrical leads.

7. An electrical switch for use with a distribution transformer, comprising:

a stator having a ring-shaped contact deck, a mounting hub spaced from said contact deck by a plurality of circumferentially spaced rib members, and a plurality of stationary contacts carried by said contact deck, said mounting hub having first and second ends, an opening extending between its ends coaxial with said ring-shaped contact deck, and a mounting flange disposed between its ends, said plurality of stationary contacts being arranged into first and second spaced planes perpendicular to the common axis of said mounting hub and contact deck,

a rotor mounted for rotation within said stator, including an operating shaft having a first end which extends through the opening in said mounting hub, and a second end, an insulating contact carrier carried by the second end of said operating shaft which includes first and second movable contact assemblies, each of said movable contact assemblies having first, second and third electrically connected elements, with the first and second elements engaging stationary contacts in the first plane, and the third elements engaging stationary contacts in the second plane, when the operating shaft is actuated.

8. The electrical switch of claim 7 including a handle fixed to the first end of the operating shaft for selectively engaging the desired stationary and movable contacts.

9. The electrical switch of claim 8 including first and second stop means extending outwardly from the first end of the mounting hub, which cooperate with a first portion of the handle to set the rotational operating limits of the rotor.

10. The electrical switch of claim 9 including at least one opening disposed in the first end of the mounting hub adapted to receive a pin for cooperating with a second portion of the handle to further restrict the rotational movement of the rotor.

11. The electrical switch of claim 8 including a plurality of circumferentially spaced openings disposed in the first end of the mounting hub, which are aligned with the different positions of the electrical switch, and an opening through the handle aligned with the openings in the first end of the mounting hub at each position of the electrical switch, said aligned openings in the handle and mounting hub being adapted to receiving a locking member to prevent the tap changing switch from being moved from a selected position.

12. The electrical switch of claim 7 including an annular groove disposed in the face of the mounting flange, adapted to receive a sealing gasket, said annular groove being located such that the casing of the apparatus that the switch is adapted to be mounted with contacts the flange on both sides of the annular groove, to provide a predetermined maximum compression of a sealing gasket disposed therein.

13. The electrical switch of claim 7 wherein the stationary contacts are of the single knife-blade type. and the elements of the movable contacts each include two fingerlike contacts biased together.

14. The electrical switch of claim 13 wherein the fingerlike contacts of the movable contacts are substantially V-shaped. with the stationary contacts having depressions therein which cooperate with the bottom edges of the V-shaped contacts to provide a detent action when the stationary and movable contacts are properly engaged.

15. The electrical switch of claim 7 wherein the stationary contacts disposed in the first plane are circumferentially spaced a predetermined distance apart, and the stationary contacts disposed in the second plane fall on a line which lies midway between predetermined adjacent stationary contacts of the first plane. to provide the maximum electrical clearance between the stationary contacts of the two spaced planes.

16. The electrical switch of claim 7 wherein the stator includes a plurality of similar contact decks, all disposed coaxially with the mounting hub, and all including stationary contacts disposed in first and second spaced planes. and the rotor includes a like numbered plurality of insulating contact carriers each having first and second movable contact assemblies, with the contact assemblies of each insulating contact carrier cooperating with the stationary contacts of a different contact ring. 

1. An electrical switch for use with a distribution transformer, comprising: a stator portion having a central axis, a ring-shaped contact deck coaxial with the central axis, and a plurality of stationary contacts arranged on said ring-shaped contact deck in first and second spaced planes perpendicular to the central axis, provided by a substantially planar surface of said ringshaped contact deck, and the ends of a plurality of circumferentially spaced projections on the planar surface, respectively, said stationary contacts having an elongated configuration with their ends extending radially inward and outward from said ring-shaped contact deck, and a rotor portion coaxially positioned within said stator portion for rotational movement relative thereto, said rotor portion having first and second contact assemblies each having first, second and third electrically connected contact elements, the first and second contact elements of each contact assembly are disposed to engage the inwardly extending ends of the stationary contacts disposed in one of the planes, and the third contact element of each contact assembly is disposed to engage an inwardly extending end of a stationary contact disposed in the other plane, when said rotor portion is rotated relative to said stator portion.
 2. The electrical switch of claim 1 wherein the stationary contacts of the first plane are circumferentially spaced about a first circle coaxial with the central axis of the stator portion, and the stationary contacts of the second plane are disposed about a second circle coaxial with the first circle, with the contacts of the second plane being located on a line which is midway between certain of the stator contacts of the first plane.
 3. THe electrical switch of claim 2 wherein the first and second contact elements of each of the first and second contact assemblies are spaced to simultaneously engage two circumferentially adjacent stationary contacts of one of the planes, and the third contact element of each of the first and second contact assemblies is disposed midway between the first and second contact elements, but axially spaced therefrom, to engage a stationary contact of the other plane when one is disposed between the two stationary contacts engaged by the first and second contact elements of the contact assembly.
 4. The electrical switch of claim 1 wherein the stationary contacts have first and second ends, with the first end being a knife blade type contact, and wherein the contact elements of the first and second contact assemblies each include two fingerlike contacts biased together, said knife blade type stationary contact forcing the fingerlike contacts of the contact elements apart when in engagement therewith.
 5. An electrical switch for use with a distribution transformer, comprising: a stator portion having a central axis, and a plurality of stationary contacts arranged about the central axis in first and second spaced planes perpendicular to the central axis, and a rotor portion coaxially positioned within said stator portion for rotational movement relative thereto, said rotor portion having first and second contact assemblies each having first, second and third electrically connected contact elements, the first and second contact elements of each contact assembly are disposed to engage stationary contacts disposed in the first plane, and the third contact element of each contact assembly is disposed to engage stationary contacts disposed in the second plane, when said rotor portion is rotated relative to said stator portion, said stationary contacts having first and second ends, with the first end being a knife blade type contact, and wherein the contact elements of the first and second contact assemblies each include two fingerlike contacts biased together, said knife blade type stationary contact forcing the fingerlike contacts of the contact elements apart when in engagement therewith, said fingerlike contacts of the contact elements being substantially V-shaped and the stationary contacts having depressions therein which cooperate with the bottom edges of the V-shaped fingerlike contacts to provide a detent action when the contacts engage.
 6. An electrical switch for use with a distribution transformer, comprising: a stator portion having a central axis, and a plurality of stationary contacts arranged about the central axis, and a rotor portion coaxially positioned within said stator portion for rotational movement relative thereto, said rotor portion having first and second contact assemblies each having first, second and third electrically connected contact elements, the first and second contact elements of each contact assembly are disposed to engage stationary contacts disposed in the first plane, and the third contact element of each contact assembly is disposed to engage stationary contacts disposed in the second plane, when said rotor portion is rotated relative to said stator portion, said stationary contacts having first and second ends, with the first end being a knife blade type contact, and wherein the contact elements of the first and second contact assemblies each include two fingerlike contacts biased together, said knife blade type stationary contact forcing the fingerlike contacts of the contact elements apart when in engagement therewith, the second ends of the stationary contacts each being divided to provide two terminals adapted for connection to external electrical leads.
 7. An electrical switch for use with a distribution transformer, comprising: a stator having a ring-shaped contact deck, a mounting hub spaced from said contact deck by a plurality of circumferentially spaced rib members, and a plurality of Stationary contacts carried by said contact deck, said mounting hub having first and second ends, an opening extending between its ends coaxial with said ring-shaped contact deck, and a mounting flange disposed between its ends, said plurality of stationary contacts being arranged into first and second spaced planes perpendicular to the common axis of said mounting hub and contact deck, a rotor mounted for rotation within said stator, including an operating shaft having a first end which extends through the opening in said mounting hub, and a second end, an insulating contact carrier carried by the second end of said operating shaft which includes first and second movable contact assemblies, each of said movable contact assemblies having first, second and third electrically connected elements, with the first and second elements engaging stationary contacts in the first plane, and the third elements engaging stationary contacts in the second plane, when the operating shaft is actuated.
 8. The electrical switch of claim 7 including a handle fixed to the first end of the operating shaft for selectively engaging the desired stationary and movable contacts.
 9. The electrical switch of claim 8 including first and second stop means extending outwardly from the first end of the mounting hub, which cooperate with a first portion of the handle to set the rotational operating limits of the rotor.
 10. The electrical switch of claim 9 including at least one opening disposed in the first end of the mounting hub adapted to receive a pin for cooperating with a second portion of the handle to further restrict the rotational movement of the rotor.
 11. The electrical switch of claim 8 including a plurality of circumferentially spaced openings disposed in the first end of the mounting hub, which are aligned with the different positions of the electrical switch, and an opening through the handle aligned with the openings in the first end of the mounting hub at each position of the electrical switch, said aligned openings in the handle and mounting hub being adapted to receiving a locking member to prevent the tap changing switch from being moved from a selected position.
 12. The electrical switch of claim 7 including an annular groove disposed in the face of the mounting flange, adapted to receive a sealing gasket, said annular groove being located such that the casing of the apparatus that the switch is adapted to be mounted with contacts the flange on both sides of the annular groove, to provide a predetermined maximum compression of a sealing gasket disposed therein.
 13. The electrical switch of claim 7 wherein the stationary contacts are of the single knife-blade type, and the elements of the movable contacts each include two fingerlike contacts biased together.
 14. The electrical switch of claim 13 wherein the fingerlike contacts of the movable contacts are substantially V-shaped, with the stationary contacts having depressions therein which cooperate with the bottom edges of the V-shaped contacts to provide a detent action when the stationary and movable contacts are properly engaged.
 15. The electrical switch of claim 7 wherein the stationary contacts disposed in the first plane are circumferentially spaced a predetermined distance apart, and the stationary contacts disposed in the second plane fall on a line which lies midway between predetermined adjacent stationary contacts of the first plane, to provide the maximum electrical clearance between the stationary contacts of the two spaced planes.
 16. The electrical switch of claim 7 wherein the stator includes a plurality of similar contact decks, all disposed coaxially with the mounting hub, and all including stationary contacts disposed in first and second spaced planes, and the rotor includes a like numbered plurality of insulating contact carriers each having first and second movable contact assemblies, with the contact assemblies of each insulating contact carrier cooperating with the stationary coNtacts of a different contact ring. 